Current theories in psychology now suggest that behaviours that were primarily associated with psychotic disorders, such as delusional experiences, can be observed in the healthy general population (van Os, Linscott, Myin-Germeys, Delespaul and Krabbendam, 2009). Delusions, a common symptom of schizophrenia, have been associated with a tendency to jump to conclusions. In simpler terms, it has been discussed that those that experience delusions will reach final decisions earlier than controls upon the basis of little evidence (Huq, Garety and Hemsley, 1988). The aim of the research was to investigate the factors that may moderate this susceptibility to jump to conclusions amongst the sub-clinical range of delusional thinking amongst the distinct construct measures of the Peters et al. Delusions Inventory (PDI: Peters, Day and Garety, 1996). Numerous studies were conducted to investigate: intelligence, probability calculation ability, experimental task design and task delivery upon the emergence of the jump to conclusions bias (Chapters II-VI). Moderator analyses identified that task design and task delivery were strong predictors of the quantity of information requested prior to finalising a decision; with restricted data gathering occurring with the use of face-to-face abstract tasks (Chapter III and VI B). When tasks included neutral and emotionally-unstimulating material, a data gathering bias was either not observed (Chapter II) or data gathering was enhanced amongst those with high belief conviction. Perceived life stress, perceived task stress and specific reasoning styles were investigated in an attempt to explain the situation-specific differences (Chapters VII and VIII). It was concluded in the General Discussion that delusional thinking appears to be associated with hasty decision making, under specific situational circumstances and can differ between the distinct constructs of the PDI measure (Peters et al. 1996). Sub-clinical delusional ideation is an overall summation of belief distress, preoccupation and conviction. The current research argues that the three psychological dimensions of delusional belief can influence decision making uniquely; specifically in relation to the emergence of a data gathering bias.